Fiber based products used as packages must both be able to protect the packed product from outer influences as well as withstand the influence of the packed product. One way to achieve the desired protection is to provide the package with a barrier.
In the case of perishable products, such as oxygen sensitive products, oxygen barrier characteristics of the package are required to provide extended shelf life for the packaged product. By limiting the exposure of oxygen-sensitive products to oxygen, the quality and shelf life of many products are maintained and enhanced. For instance, by limiting the oxygen exposure of oxygen-sensitive food products in a packaging system, the quality of the food product can be maintained and spoilage retarded. In addition, such packaging also keeps the product in inventory longer, thereby reducing costs incurred from waste and having to restock.
Barriers against for example liquids and/or grease can be used in order to increase the package's resistance of the packed product.
Barriers are normally created by coating the fiber based substrate with a composition which gives the substrate barrier properties. Different coatings can be applied depending on the needed properties of the barrier. The most commonly used materials when forming a barrier on a fiber based product, are polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), ethylene vinyl alcohol (EVOH) or ethylene vinyl acetate (EVA). EVOH is normally used in order to create oxygen barriers and PE or PET is normally used in order to create a liquid and/or vapor barrier. The polymers are normally either laminated or extrusion coated to the fiber based product.
However, the thickness of a polymer layer which gives a product barrier properties normally need to be very thick and it is quite costly to produce such barrier product.
Another commonly used material in order to produce a barrier is aluminum. A layer comprising aluminum is above all used in order to improve the oxygen and light barrier of a paper or paperboard product. The thickness of an aluminum layers is normally quite thin, often around 7-9 μm. Aluminum gives excellent barrier properties but it strongly increases the carbon dioxide load of the product. Furthermore, aluminum decreases the possibility to recycle the package. There is therefore a demand from both producers and end users to avoid the use of aluminum layers in paper or paperboard products in order to decrease the carbon dioxide load of a product.
There is still a need for an improved fiber based product with barrier properties which is both more economical beneficial to produce and which can be produced at a low carbon dioxide load.